222 



ZOOLOGY. 



insertion of the muscles it enlarges, but there is no true 

 stomach ; it is about twice the length of the body, and is bent 



and twisted on itself, ending 

 dorsally in a vent marked by an 

 external wart, on the anterior 

 third of the body. Near this 

 point is situated a pair of large, 

 long, slightly twisted segmental 

 organs(s)the free ends of which 

 flare slightly. The nervous 

 system (n) forms an cesophageal 

 ring, and from it passes a well- 

 marked ventral single cord, 

 from which at short intervals 

 pass off small short lateral 

 nerves. The vascular system 

 is represented by a circular 

 vessel lying next to the ner- 

 vous oasophageal ring, sending 

 branches into, or at least in 

 communication with, the cavi- 

 ties of the tentacles, and from 

 the ring passing along and in- 

 timately connected with the di- 

 gestive tract, forming a ruffle- 

 like organ (v), ending at a point 

 nearly opposite the vent (a). 

 Prof. Greef finds that the vas- 

 cular system of EcMurus con- 

 sists of two main vessels, i. e., 

 _ a dorsal and a ventral vessel ; 



Fig. i4fl.-A^my of Pkascotosoma the f ormer extending along the 



alimentary canal, and ending 



The 



muscles ; pr, two long retractor mus- a branch to the proboscis, where 



cles; v, next to a dark line the right . . , , 



side of the long oesophagus indicating it divides lllto two branches, 



the water-vascular tube ; n, nervous , ... . , . , , 



cord ; , segmental organs ; the long, each uniting With the VClltral 



twisted intestine returns, ending at a. -i mi -i-, -i -i -i 



Natural size.-Drawn by J. S. Kings- VCSSel. The blood IS pale yel- 



lowish, with corpuscles. 



blood-system of the Gephyrea, then, is homologous with 



